How can you tell if a BACnet Value is in Manual Override?

I am trying to find a way to display is a Read / Write BACnet Value has been overwritten to Priority 8 (Manual Override). I am using a FactoryTalk Studio / PanelView Plus along with Kepware Enterprise, to read and display a BACnet Value.

We read the Value from its Auto Value (Priority 16), and then we write to Priority 8. The value stays in Override until the Value is Relinquished, and then we are able to read the Auto Value. I want to display "Override" when the value is written to Priority 8; however, I have not been able to find a good trigger. Let me know if anyone has any experience with BACnet and Manual Overrides. Thanks.

bacnet panelview-plus kepware

asked Dec 01 '09 at 22:57

Luis R
208●1●6

2 Answers:

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If you setup another tag to read from Priority_Array at priority 8, does it give you different values depending on if you've written a value to Priority 8 vs. if you've relinquished it? If so, can you trigger off that?

Doing a little reading, it looks like it's a common problem:

For outputs, there is nothing in the object’s status flags to indicate that the point has been manually overwritten. The OWS must read the Priority_Array to determine what is controlling the object and provide indication to the operator.

(OWS refers to Operator Work Station in this case.)

link

answered Dec 03 '09 at 01:15

Scott Whitlock ♦♦
635●1●15

Using BACnet you are able to read all the priorities, as well as the Relinquish Default Value ("Auto" Value). If a value has no value in a specific Priority it will read a NULL Value. BACnet is very useful but definitely has its quirks.

(Dec 03 '09 at 20:18) Luis R

@Luis R - So can you trigger off the Null/Non-Null value?

(Dec 03 '09 at 21:14) Scott Whitlock ♦♦

I believe I have tested this before, and while it does work. It's not exactly the most viable solution. There are certain conditions that need to be reviewed for everypoint, either using code in the HMI or PLC.

(Dec 04 '09 at 16:06) Luis R

1	For the BACnet driver your only option is to monitor the PiorityArray string. Fred Loveless, Kepware link answered Dec 04 '09 at 21:11 user-39 (google) 41●1

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